Finite-length charge-density waves on terminated atomic wires

Finite-size effects in charge-density waves (CDWs) were unveiled using scanning tunneling microscopy for metallic atomic wires on the Au/Si(553) surface, as terminated by adsorbate impurities. We found that CDW formed at low temperature adopts the finite-length boundary condition in two distinct ways, depending on the length scale. For longer wires than ~10 nm, the CDW correlation length, the decay length of the CDW amplitude from the terminating ends, scales continuously with the wire length as predicted in a recent hyperscaling theory [Phys. Rev. B 75, 205428 (2007) (http://dx.doi.org/10.1103/PhysRevB.75.205428)]. For shorter wires, the boundary condition becomes discrete with respect to the CDW wavelength of 3a sub(0). For incommensurate wire lengths with 3a sub(0), fluctuating CDW states were observed, which are due to the motion of solitonlike antiphase boundaries.